1. Field of the Invention
This invention relates to a multiband PLL frequency synthesizer for generating a frequency signal over a plurality of bands.
2. Description of the Prior Art
A multiband PLL frequency synthesizer for generating a frequency signal over a plurality of bands is known.
FIG. 7 is a block diagram of a prior art multiband PLL (phase-locked loop) frequency synthesizer. This prior art multiband PLL frequency synthesizer includes three PLL frequency synthesizing circuits 313, 314, and 315. The PLL frequency synthesizing circuits 313, 314, and 315 generate frequency signals at different bands respectively. FIG. 8 is an illustration of the prior art showing an example of using the prior art multiband PLL frequency synthesizer shown in FIG. 7. In FIG. 8. the PLL frequency synthesizing circuits 313, 314, and 315 generate frequency signals at bands f1 to f2, f3 to f4, and f5 to f6 respectively. A switch 316 outputs one of the frequency signals from the PLL frequency synthesizing circuits 313, 314, and 315.
In this circuit, there are many parts used because three similar circuits are used.